Safety device for a pre-filled syringe and injection device

ABSTRACT

According to the invention a safety device for a pre-filled syringe comprises a substantially cylindrical and hollow support body and a hollow needle shield slideably arranged relative to the support body. The support body comprises at least one resilient arm and the hollow needle shield or a needle shield assembly comprises at least one curved actuation ramp. The curved actuation ramp protrudes in a lateral direction (L) perpendicular to a central axis (A) of the safety device. The curved actuation ramp comprises a first lateral dimension (L 1 ) at a proximal end of the needle shield and a second lateral dimension (L 2 ) exceeding the first lateral dimension (L 1 ) at a distal end of the needle shield. The resilient arm engages the curved actuation ramp when the needle shield is slid relative to the support body.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. National Phase Application pursuant to35 U.S.C. §371 of International Application No. PCT/EP2011/060320 filedJun. 21, 2011, which claims priority to European Patent Application No.10168319.1 filed on Jul. 2, 2010. The entire disclosure contents ofthese applications are herewith incorporated by reference into thepresent application.

FIELD OF INVENTION

The present invention relates to safety devices that provide needlesafety and more particularly to safety devices for pre-filled syringes.The safety device is adapted to avoid accidental needle pricks andneedle injuries before, during and after an injection of a medication ordrug contained in the pre-filled syringe. In particular, the safetydevice provides needle safety for a subcutaneous self-administratedinjection or for an injection administered by a health-careprofessional. The present invention further relates to injection devicescomprising a pre-filled syringe.

BACKGROUND

Pre-filled syringes that are filled with a selected dosage of amedication are well known injection devices for administering themedication to a patient. Safety devices for covering a needle of apre-filled syringe before and after use are also well known. Typically,these devices comprise a needle shield that is either manually moved ormoved by the action of a relaxing spring to surround the needle.

A different type of safety devices known in the state of the art solvethe object of providing needle safety by arranging the pre-filledsyringe movable relative to a body, whereas the pre-filled syringe isretracted into the body after the injection.

SUMMARY

It is an object of the present invention to provide an improved safetydevice for a pre-filled syringe.

It is a further object of the invention to provide an improved injectiondevice comprising a pre-filled syringe that is safe to handle and inparticular prevents accidental needle stick injuries.

The object is achieved by a safety device according to claim 1 and by aninjection device according to claim 12.

Preferred embodiments of the invention are given in the dependentclaims.

In the context of this specification, the terms distal and proximal aredefined from the point of view of a person performing an injection.Consequently, a distal direction refers to a direction pointing towardsthe body of patient receiving an injection and a distal end defines anend of an element that is directed towards the body of the patient.Respectively, the proximal end of an element or the proximal directionis directed away from the body of the patient receiving the injectionand opposite to the distal end or distal direction.

According to the invention, a safety device for a pre-filled syringecomprises a substantially cylindrical and hollow support body and ahollow needle shield slideably arranged relative to the support body.The support body comprises at least one resilient arm and the hollowneedle shield or a needle shield assembly comprises at least one curvedactuation ramp. The curved actuation ramp protrudes in a lateraldirection perpendicular to a central axis of the safety device. Thecurved actuation ramp comprises a first lateral dimension at a proximalend of the needle shield and a second lateral dimension exceeding thefirst lateral dimension at a distal end of the needle shield. Theresilient arm engages the curved actuation ramp when the needle shieldis slid relative to the support body.

The curved actuation ramp gives the safety device a tapered shape thatdiffers from typical designs of safety devices for pre-filled syringes.The safety device according to the present invention has a trumpet-likedesign that is in general not associated by a typical user with theunpleasant act of receiving an injection. The design of the safetydevice thus alleviates a possible fear of receiving an injection. Thisis particularly useful in the context of self-administered injections,as a fear of needles or injections might keep the patient fromperforming the injection properly.

According to a possible embodiment of the invention, the curvedactuation ramp is integrated to the needle shield.

In an alternative embodiment of the invention, the curved actuation rampis separate part connected to the needle shield. A needle shieldassembly constitutes the needle shield and the curved actuation ramp.

According to a possible embodiment of the invention, the resilient armacts as a spring means to bias the needle shield with respect to thesupport body in the distal direction and it is made from a plasticsmaterial. The safety device does not comprise any metallic part and iscompletely made from plastics materials, so that the safety device canbe cost-efficiently manufactured in high quantities. The safety deviceis well suited in combination with disposable syringes and is disposedwith the pre-filled syringe retained within the safety device after afirst use.

Preferably, the resilient arm is integrally formed to the support body.The resilient arm acts as a biasing means integral with the supportbody. The safety device comprises only a few parts made from plasticsmaterials, so that the production costs of the safety device aresignificantly reduced in comparison to typical safety devices thatcomprise regular metal springs.

The resilient arm is non-energized in a rest position and extendsessentially parallel to the central axis and over a substantial axiallength of the support body in the rest position. The resilient armprovides a simple mechanism for the biasing means of the safety devicethat is stressed and energized during use of the safety device.

According to another possible embodiment of the invention, the needleshield is movable with respect to the support body from an initialposition to a retracted position and further to an advanced position.The needle shield protrudes the support body in the initial position andin the advanced position to surround a hypodermic needle of thepre-filled syringe retained within the safety device. The needle shieldis substantially received within the support body in the retractedposition.

According to yet another possible embodiment, the needle shield is madefrom an opaque plastics material. The hypodermic needle is hidden fromthe view of the patient before the injection by the needle shield thatis retained in the initial position. This eases a possible fear ofneedles of the patient. The safety device is thus particularly suitedfor performing self-administered injections.

According to an alternative embodiment, the needle shield is made from atransparent plastics material. A healthcare professional that uses thesafety device thus can visually confirm the correct placement of thehypodermic needle penetrating the skin of the patient, even when thehypodermic needle is surrounded by the needle shield.

As the safety device is both suited for self-administered injections andinjections carried out by a healthcare professional, the person referredto as the user or the patient may be one and the same person.

When the needle shield is moved from the initial position to theretracted position, the resilient arm engages the curved actuation rampand travels along an outer edge of the curved actuation ramp. When theneedle shield reaches the retracted position, the resilient arm is bentin the lateral direction in a way that corresponds to a curvature of thecurved actuation ramp. The resilient arm thus gets stressed andenergized to bias the needle shield in the retracted position. Theresilient arm is stressed for a short time span during use of the safetydevice. This allows for the use of a plastics material prone to fatigueof material for the biasing means without having to restrict thereliability of safety device.

The resilient arm is in the rest position when the needle shield is inthe initial position. Prior to use, the needle shield is retained in theinitial position, so that the resilient arm is in its un-stressed restposition. A fatigue of material and/or a memory effect leading to alimited flexibility of the resilient arm is thus avoided even afterprolonged periods of storage.

According to yet another possible embodiment of the invention, thecurved actuation ramp is integral formed to the needle shield, so thatthe safety device only comprises a low number of parts to lowerproduction costs.

According to yet another embodiment, the needle shield comprises askin-contact flange that rests onto the skin of the patient during theinjection of a medication contained in the pre-filled syringe. Theskin-contact flange facilitates the correct placement of the hypodermicneedle, so that in particular an unskilled user may perform a properinjection. Furthermore, the skin-contact flange is pressed towards theskin surface of the patient during the injection. The skin-contactflange comprises an increased surface area to spread the load and theinjection may be comfortably carried out.

According to yet another possible embodiment, the needle shieldcomprises two laterally protruding curved actuation ramps that protrudeopposite sides of the needle shield. This ensures that the biasing forceexerted on the needle shield by the biasing arm is directed parallel tothe central axis of the safety device. In particular, this prevents ajamming of the needle shield within the support body when the needleshield is moved from the retracted position to the advanced position bythe action of the relaxing resilient arm.

The safety device comprises a substantially cylindrical outer body thatis slideably arranged with respect to the support body. The outer bodyis slid with respect to the support body to expel the medicationcontained in the pre-filled syringe that is retained within the supportbody of the safety device. The outer body comprises at least one axialslot sized to receive the resilient arm and/or the curved actuationramp. The resilient arm and/or the curved actuation ramp protrudesthrough the axial slot when the support body is received within theouter body at the end of the injection stroke.

An injection device comprises a pre-filled syringe and a safety device.The pre-filled syringe comprises a hypodermic needle attached to adistal end of the pre-filled syringe, a barrel with an inner cavity influid communication with the hypodermic needle and a pistonfluid-tightly sealing a proximal end of the inner cavity. The piston ismovable by actuating a piston rod protruding a proximal end of thebarrel. The safety device for the pre-filled syringe comprises asubstantially cylindrical and hollow support body and a hollow needleshield slideably arranged relative to the support body. The support bodycomprises at least one resilient arm. The needle shield comprises atleast one curved actuation ramp protruding in a lateral directionperpendicular to a central axis of the safety device. The curvedactuation ramp comprises a first lateral dimension at a proximal end ofthe needle shield and a second lateral dimension exceeding the firstlateral dimension at a distal end of the needle shield. The resilientarm engages the curved actuation ramp when the needle shield is slidrelative to the support body. The hypodermic needle protrudes the distalend of the support body and is surrounded by the needle shield in aninitial position and/or in an advanced position.

The injection device comprising the pre-filled syringe and the safetydevice combines the aforementioned advantages and avoids inadvertentneedle stick injuries before, during and after an injection deliveringthe medication beneath the skin of patient.

Details of the present invention are described hereinafter. However, itshould be understood that the detailed description and the specificexamples indicate possible embodiments of the invention and are given byway of illustration only. Various changes and modifications of theillustrated embodiments within the spirit and scope of the invention areappreciated by those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the detaileddescription given in the following. The accompanying drawings are givenfor illustrative purposes only and do not limit the scope of the presentinvention.

FIG. 1 shows a perspective view of an injection device with a safetydevice for a pre-filled syringe prior to use.

FIG. 2 shows a sectional view of the injection device with a safetydevice for a pre-filled syringe with a needle shield retained in aninitial position.

FIG. 3 shows a sectional view of the injection device with a safetydevice for a pre-filled syringe with a needle shield retained in aretracted position, whereas a resilient arm is stressed and energized.

FIG. 4 shows a sectional view of the injection device with a safetydevice for a pre-filled syringe at the end of an injection stroke.

FIG. 5 shoes a sectional view of the injection device with a safetydevice with the needle shield retained in an advanced position.

FIG. 6 shows a perspective view of a support body and a needle shield ofa safety device, whereas the needle shield is retained in an advancedposition.

FIG. 7 shows a sectional view of an injection device with a safetydevice after an injection has been performed.

FIG. 8A to 8F show details of a guide track and the movement of a guidepin within the guide track during use of the safety device.

Corresponding parts are marked with the same reference symbols in allfigures.

DETAILED DESCRIPTION

FIG. 1 shows an injection device D with a safety device 1 for apre-filled syringe 2 as it would be presented to a user performing aninjection. The safety device 1 comprises a hollow needle shield 1.1. Theneedle shield 1.1 is received within a substantially hollow support body1.2, whereas the needle shield 1.1 is slidable with respect to thesupport body 1.2. Prior use of the safety device 1, the needle shield1.1 is retained in an initial position I, wherein the needle shield 1.1protrudes the support body 1.2.

A circumferential skin-contact flange 1.1.1 is formed to the needleshield 1.1 at its distal end. The skin-contact flange 1.1.1 is adaptedto be pressed against the skin of a patient and protrudes radialoutwardly and perpendicular to a central axis A of the safety device 1.Edges of the skin-contact flange 1.1.1 that come into contact with theskin of the patient are rounded to avoid injuries. The skin-contactflange 1.1.1 has a central opening centred on the central axis A of thesafety device 1. The skin-contact flange 1.1.1 is integral to the needleshield 1.1, or, alternatively, a separate part attached to the needleshield 1.1 that is made from a plastics material.

The needle shield 1.1 comprises two curved actuation ramps 1.1.2 thatprotrude two opposite sides of the needle shield in a lateral directionperpendicular to a central axis A of the safety device 1. Each curvedactuation ramp 1.1.2 has a first lateral dimension L1 at a proximal endof the needle shield 1.1 and a second lateral dimension L2 at a distalend of the needle shield 1.1. The second lateral dimension L2 of theactuation ramp 1.1.2 exceeds the first lateral dimension L1 of theactuation ramp 1.1.2.

The curved actuation ramp 1.1.2 is arranged with the needle shield 1.1as one piece, or alternatively, a separate part made from a plasticsmaterial that is connected to the needle shield 1.1. In this alternativeembodiment, a needle shield assembly comprises the needle shield 1.1 andthe curved actuation ramp 1.1.2 connected to the needle shield 1.1.

A guide pin 1.1.3 is integrally formed to a flexible arm 1.1.4 of theneedle shield 1.1. The flexible arm 1.1.4 extends in its rest positionessentially parallel to the central axis A of the safety device 1. Asillustrated in FIG. 1, the guide pin 1.1.3 protrudes radial outwardlyinto a guide track 1.2.1 formed into the substantially cylindricalsupport body 1.2. A trapezoid cut-out 1.1.5 is formed into the needleshield 1.1 adjacent to the flexible arm 1.1.4 to allow for a deflectionand pivoting movement of the flexible arm 1.1.4. Prior to use of thesafety device 1, the guide pin 1.1.3 is retained within an inclinedsection 1.2.1.1 of the guide track 1.2.1 in a start position PI locatedat a distal end of the guide track 1.2.1. As the flexible arm 1.1.4 isin the rest position, the guide pin 1.1.3 is laterally non-biased in thestart position PI. The inclined section 1.2.1.1 is oriented at an acuteangle relative to the cylindrical axis A of the safety device 1.

The needle shield 1.1 is retained in an initial position I by the guidepin 1.1.3 being retained in a start position PI in the inclined section1.2.1.1 of the guide track 1.2.1. The needle shield 1.1 is made from anopaque plastics material, so that a hypodermic needle 2.1 of thepre-filled syringe 2 retained within the safety device 1 is hidden fromview of the patient before the injection.

Alternatively, the needle shield 1.1 is made from a transparent plasticsmaterial, so that a healthcare professional performing the injection mayvisually confirm the correct placement of the hypodermic needle 2.1before penetrating the skin of the patient.

The guide pin 1.1.3 is prevented from leaving the start position PI byan interaction of several components of the safety device 1: Upondeflection, the flexible arm 1.1.4 biases the guide pin 1.1.3 in thelateral direction L back towards the start position PI. The guide pin1.1.3 abuts the distal end of the inclined section 1.2.1.1 in thelateral direction L and distal direction.

The guide track 1.2.1 comprises a widened section 1.2.1.2 extendingparallel to the central axis A of the safety device 1. A flexibleseparating wall 1.2.2 extends parallel to the central axis A and intothe widened section 1.2.1.2 from a distal direction. The flexibleseparating wall 1.2.2 is integral part with the support body 1.2 andacts as a no-return feature preventing the guide pin 1.1.3 fromreturning to its start position PI after an injection stroke has atleast partially been carried out. Furthermore, the flexible separatingwall 1.2.2 guides the movement of the guide pin 1.1.3 within the guidetrack 1.2.1, so that the guide pin 1.1.3 is prevented to enter an endposition PIII from the distal direction but allowed to enter from theproximal direction. The end position PIII is defined by a generallyU-shaped indent between the distal and a proximal end of the guide track1.2.1.

The support body 1.2 is made from a resilient plastics material. Thesupport body 1.2 is slotted along a substantial longitudinal lengthparallel to the central axis A, so that two resilient arms 1.2.3 areformed to opposite sides of the support body 1.2. Each resilient arm1.2.3 protrudes the support body 1.2 in a radial outward direction. Theresilient arm 1.2.3 acts as a spring means of the safety device 1,whereas the resilient arm 1.2.3 biases the support body 1.2 and theneedle shield 1.1 away from each other when these parts 1.1, 1.2 areslid relative to each other during the injection.

Alternatively, the resilient arms 1.2.3 may be separate plastics partsthat are connected to each other by a collar that is retained within andaffixed to the support body 1.2

The safety device 1 comprises an essentially cylindrical and hollowouter body 1.3 made from a plastics material with an open distal and aclosed proximal end. The proximal end of the support body 1.2 isreceived within the open distal end of the outer body 1.3, whereas theouter body 1.3 is slidable with respect to the support body 1.2 in adistal direction to substantially receive the support body 1.2 insidethe outer body 1.3.

A circumferential and outwardly protruding hand flange 1.3.1 isintegrally formed to an exterior surface of the outer body 1.3 close toits distal end.

Furthermore, two opposing axial slots 1.3.3 are formed into oppositesides of the outer body 1.3 that receive the outwardly protrudingresilient arms 1.2.3 and the curved actuation ramps 1.1.2 when theneedle shield 1.1, the support body 1.2 and the outer body 1.3 are slidrelative to each other during the injection.

A clamp arm 1.3.4 is formed into the substantially cylindrical outerbody 1.3 that is deflectable in the radial direction perpendicular tothe central axis A. As best seen in FIG. 7, the clamp arm 1.3.4comprises an inwardly protruding locking catch 1.3.4.1 that is sized tofit into a locking recess 1.2.5 formed into the support body 1.2 inproximity of a proximal end of the support body 1.2.

The injection device D comprises the safety device 1 with the pre-filledsyringe 2 retained within the support body 1.2. FIG. 2 shows thepre-filled syringe 2 received within the support body 1.2 that comprisesa hypodermic needle 2.1 covered by a needle cap 2.2 frictionally affixedto a distal end of a barrel 2.3. The barrel 2.3 has an inner cavity2.3.1 containing a medication. The inner cavity 2.3.1 is in fluidcommunication with the hypodermic needle 2.1. A proximal end of theinner cavity 2.3.1 is fluid-tightly sealed by a piston 2.4 that isconnected to a piston rod 2.5. The piston 2.4 is movable in at least thedistal direction by actuating the piston rod 2.5 protruding the barrel2.3 in the proximal direction. The barrel 2.3 of the pre-filled syringe2 comprises a barrel collar 2.3.2 that abuts a radial inwardlyprotruding inner surface of the support body 1.2 at its proximal endaffixing the pre-filled syringe 2 to the support body 1.2.

With cross-reference to FIG. 6, it can be seen that the support body 1.2comprises clips 1.2.6 that engage the barrel collar 2.3.2 to retain thepre-filled syringe 2 within the support body 1.2.

The pre-filled syringe 2 is retained within the support body 1.2,whereby the hypodermic needle 2.1 protrudes the support body 1.2 in thedistal direction.

In the packaged state as shown in FIGS. 1 and 2, the hypodermic needle2.1 is covered by needle cap 2.2 that is surrounded by the needle shield1.1 prior to use of the injection device D. The needle cap 2.2 ispreferably at least partially made from a plastics material like rubber.The width of the central opening of the skin-contact flange 1.1.1corresponds to an outer diameter of the needle cap 2.2. A needle capremover 3 is inserted into the central opening of the skin-contactflange 1.1.1 and protrudes the skin-contact flange 1.1.1 in a distaldirection, so that the user can easily remove the needle cap 2.2 fromthe pre-filled syringe 2 by pulling the needle cap remover 3 in thedistal direction. The needle cap remover 3 comprises clamp means 3.1that clamp to a distal end of the needle cap 2.2.

Alternatively, the injection device D comprising the safety device 1with the pre-filled syringe 2 retained therein is shipped and deliveredto an end-user with a needle cap remover 3 attached to the distal end ofthe needle cap 2.2 retained within the safety device 1, so that theneedle cap remover 3 protrudes the needle shield 1.1 in the distaldirection.

As shown in FIG. 2, a proximal end of the piston rod 2.5 abuts theclosed distal end of the outer body 1.3, so that the piston 2.4 ismovable in a distal direction by the distal displacement of the outerbody 1.3 with respect to the support body 1.2.

Alternatively, the piston rod 2.5 is connected to the outer body 1.3 oran integral to the outer body 1.3. This alternative embodiment hasadditional advantage of a low overall part count, so that manufacturingcosts are reduced.

The needle shield 1.1 is in the initial position I surrounding thehypodermic needle 2.1 of the pre-filled syringe 2.

FIG. 3 shows a sectional view of the injection device D with the safetydevice 1 at the beginning of an injection stroke. The needle shield 1.1is in the retracted position II, wherein the needle shield 1.1 issubstantially received within the support body 1.2. The hypodermicneedle 2.1 distally protrudes the skin-contact flange 1.1.1 of theneedle shield 1.1. The resilient arm 1.2.3 engaging the curved actuationramp 1.1.2 is outwardly bent in the lateral direction L and is curvedcorresponding to the curvature of the curved actuation ramp 1.1.2. Theresilient arm 1.2.3 is in a maximally stressed state to bias the needleshield 1.1 with respect to the support body 1.2 in the distal direction.

FIG. 4 shows a sectional view of the injection device D with the safetydevice 1 at the end of the injection stroke. The needle shield 1.1 is inthe retracted position II, wherein the needle shield 1.1 issubstantially received within the support body 1.2. The guide pin 1.1.3that is integral to the needle shield 1.1 is in an intermediate positionPII within the guide track 1.2.1 in proximity of a proximal end thereof.The intermediate position PII of the guide pin 1.1.3 within the guidetrack 1.2.1 corresponds to the retracted position II of the needleshield 1.1.

FIG. 5 shows a sectional view of the injection device D with the safetydevice 1 after the injection of the medication. The needle shield 1.1 isin an advanced position III protruding distally from the support body1.2, whereas the hypodermic needle 2.1 is surrounded by the needleshield 1.1 to avoid needle accidental needle injuries. The needle shield1.1 is fixed to the advanced position III by the guide pin 1.1.3 beingretained in the end position PIII.

The resilient arms 1.2.3 are in their rest position and extendsubstantially parallel to the cylindrical axis A. The support body 1.2is substantially received within the outer body 1.3.

FIG. 6 shows a perspective view of the needle shield 1.1 retained withrespect to the support body 1.2 in the advanced position III. Thesupport body 1.2 comprises two clips 1.2.6 diametrical opposite to eachother. The clips 1.2.6 are located near the proximal end of the supportbody 1.2 and clamp to the collar 2.3.2 of the pre-filled syringe 2 toaffix the pre-filled syringe 2 to the support body 1.2, so that thepre-filled syringe 2 is firmly retained within the support body 1.2.

Two longitudinal recesses (not illustrated) are formed into the oppositesides of an inner surface of the outer body 1.3. The longitudinal recessextends over a substantial axial length of the outer body 1.3 andparallel to the central axis A. Each longitudinal recess receives acorresponding outward projection (not illustrated) formed to a proximalend of the support body 1.2. The outward projection moves within thelongitudinal recess when the outer body 1.3 is slid relative to thesupport body 1.2 to perform the injection stroke, whereby a rotation ofthe outer body 1.3 relative to the support body 1.2 is prevented. Priorto use of the safety device 1, the outward projection abuts a distal endof the longitudinal recess to limit a proximal movement of the outerbody 1.3 with respect to the support body 1.2.

FIG. 7 shows a sectional view of the safety device 1, whereas the planesection shown extends essentially perpendicular to the cross-sectionshown in FIG. 5. The piston 2.4 is fully depressed inside the barrel 2.3of the pre-filled syringe 2. The support body 1.2 is received within theouter body 1.3 and locked to it, so that a re-usage of the safety device1 is prevented. The inwardly protruding locking catch 1.3.4.1 formed tothe clamp arm 1.3.4 latches to the corresponding locking recess 1.2.5formed into the support body 1.2 to irreversibly lock the support body1.2 with respect to the outer body 1.3.

FIGS. 8A to 8F show details of the guide track 1.2.1 formed into thesupport body 1.2 and the movement of the guide pin 1.1.3 within theguide track 1.2.1 during use if the safety device 1.

As shown in FIG. 8A, the guide pin 1.1.3 is retained prior to theinjection in the start position PI at the distal end of the inclinedsection 1.2.1.1 of the guide track 1.2.1, affixing the needle shield 1.1to the initial position I. In the initial position I, the hypodermicneedle 2.1 is surrounded by the needle shield 1.1.

The injection is carried out by orientating the central axis Aessentially perpendicular to the skin of the patient, whereas theskin-contact flange 1.1.1 of the needle shield 1.1 rests on the skinsurface of the patient and the proximal section of the outer body 1.3proximal of the hand flange 1.3.1 is gripped by the user performing theinjection. The hand flange 1.3.1 supports the hand of the user to carryout the injection stroke.

The injection is carried out in stages. In a first stage, the needleshield 1.1 is pushed inside the support body 1.2 in the proximaldirection against the biasing force of the resilient arms 1.2.3 actingas spring means made from a plastics material. As illustrated in FIG. 8Aand FIG. 8B, the guide pin 1.1.3 leaves its start position PI and movesalong the inclined section 1.2.1.1 of the guide track 1.2.1. As thedistal end inclined section 1.2.1.1 is oriented at an acute anglerelative to the central axis A, the movement of the guide pin 1.1.3causes the flexible arm 1.1.4 to become laterally deflected andstressed, so that the guide pin 1.1.3 is biased in a lateral directionL.

The guide pin 1.1.3 travels further along the guide track 1.2.1 in theproximal direction. As shown in FIG. 8C, the guide pin 1.1.3 enters thewidened section 1.2.1.2 of the guide track 1.2.1 and abuts the flexibleseparating wall 1.2.2 in the lateral direction L. The flexibleseparating wall 1.2.2 is laterally deflected by a force exerted upon theflexible separating wall 1.2.2 by the stressed flexible arm 1.1.4. Theelasticity of the flexible separating wall 1.2.2 is adapted tocorrespond to the elasticity of the flexible arm 1.1.4, so that theflexible separating wall 1.2.2 is deflectable by the deflected andstressed flexible arm 1.1.4.

The flexible separating wall 1.2.2 prevents the guide pin 1.1.3 fromentering the end position PIII as the guide pin 1.1.3 enters the widenedsection 1.2.1.2 from the distal direction.

The guide pin 1.1.3 moves further proximally towards an intermediateposition PII and reaches a proximal end of the flexible separating wall1.2.2, as illustrated in FIG. 8D. At this point, the safety features ofthe safety device 1 are activated, as the flexible separating wall 1.2.2relaxes and snaps back into its rest position substantially parallel tothe central axis A. From now on, the end position PIII is accessible forthe guide pin 1.1.3 to enter whereas the guide pin 1.1.3 is prevented tore-enter the start position PI. A subsequent removal of the safetydevice 1 causes the needle shield 1.1 and the guide pin 1.1.3 to advancedistally, so that the needle shield 1.1 surrounds the hypodermic needle2.1 of the pre-filled syringe in an advanced position III. The needleshield 1.1 is firmly retained in the advanced position III by the guidepin 1.1.3 being retained in the U-shaped indent of the guide track 1.2.1defining the end position PIII, whereby a re-usage of the injectiondevice D and/or the safety device 1 is prevented.

The flexible separating wall 1.2.2 has an axial dimension extendingparallel to the central axis A and into the widened section 1.2.1.2 ofthe guide track 1.2.1. The axial dimension defines a minimal axialdistance, the needle shield 1.1 has to be moved with respect to thesupport body 1.2 before the advanced position III is accessible for theneedle shield 1.1 to enter. At the same time the safety features thatprevent a re-usage of the safety device 1 are activated. Thus, anunintentional activation of the safety features of the safety device 1is avoided, when the needle shield 1.1 is accidentally pushed distallyby an axial length that is smaller than the minimal axial distance.

The safety device 1 generates an audible feedback indicating theactivation of the safety features. The audible feedback can be generatedby the flexible separating wall 1.2.2 snapping back into its restposition substantially parallel to the central axis A when the needleshield 1.1 is distally moved with respect to the support body 1.2 by anaxial length that exceeds the minimal axial distance.

In order to inject the medication, the needle shield 1.1 is movedfurther in the proximal direction until it reaches the retractedposition III illustrated in FIG. 3, whereby the guide pin 1.1.3 isretained within the guide track 1.2.1 in the intermediate position PII.The resilient arms 1.2.3 are bent corresponding to the curvature of thecurved actuation ramp 1.1.2. The resilient arms 1.2.3 are fullyenergized and stressed to bias the needle shield 1.1 with respect to thesupport body 1.2 in the distal direction. The user performing theinjection presses the skin-contact flange 1.1.1 against the biasingforce towards the skin surface of the patient, so that the hypodermicneedle 2.1 penetrates the skin of the patient and the medicationcontained in the inner cavity 2.3.1 can be injected in the followingsecond stage of the injection.

In the second stage, the outer body 1.3 moves with respect to thesupport body 1.1 in the distal direction. Simultaneously, the piston rod2.5 interacting with the outer body 1.3 is actuated to move the piston2.4 in the distal direction, whereby the medication contained in theinner cavity 2.3.1 is delivered through the hypodermic needle 2.1 andbeneath the skin of the patient.

At the end of the injection stroke, the inwardly protruding lockingcatch 1.3.4.1 formed to the clamp arm 1.3.4 latches to the correspondinglocking recess 1.2.5 formed into the support body 1.2 to irreversiblylock the support body 1.2 with respect to the outer body 1.3.

The injection device D comprising the safety device 1 with thepre-filled syringe 2 received therein is removed from the skin surface.The needle shield 1.1 immediately moves distally towards the advancedposition III by the action of the relaxing resilient arms 1.2.3. Asindicated in FIG. 8E, the guide pin 1.1.3 jointly moves with the needleshield 1.1 distally, whereby the guide pin 1.1.3 is guided by theflexible separating wall 1.2.2 towards the end position PIII.

As indicated in FIG. 8F, the guide pin 1.1.3 enters the U-shaped indentdefining the end position PIII of the guide track 1.2.1, whereby theflexible arm 1.1.4 relaxes to move the guide pin 1.1.3 laterally towardsthe end position PIII.

The guide pin 1.1.3 is firmly retained in the end position PIII, as theguide pin 1.1.3 abuts the U-shaped indent in the distal and in thelateral direction L. The flexible arm 1.1.4 is in the rest position, sothat the guide pin 1.1.3 is laterally non-biased in the end positionPIII. A lateral movement of the guide pin 1.1.3 is prevented by the formof the U-shaped indent of the guide track 1.2.1 at the end position PIIIand by the flexible arm 1.1.4. Thus, the guide pin 1.1.3 in the endposition PIII irreversibly locks the needle shield 1.1 into the advancedposition III after a single use of the safety device 1.

In one embodiment of the invention, the hypodermic needle 2.1 is hiddenfrom the view of the patient throughout the injection.

The safety device 1 presented herein provides a simple mechanism toavoid needle stick injuries. The injection is carried out by a simplelinear movement of the outer body 1.3 towards the skin of the patient,whereby the safety features that provide needle safety and preventre-usage of the safety device 1 are automatically activated. The taperedshape and design of the safety device 1 with the curved actuation ramps1.1.2 differs from typical designs of safety devices 1 for pre-filledsyringes 2 to alleviate a possible fear of injections. The safety device1, including the spring means, is exclusively made from plasticsmaterials.

1-12. (canceled)
 13. A safety device for a pre-filled syringe,comprising a substantially cylindrical and hollow support bodycomprising at least one resilient arm and a hollow needle shieldslideably arranged relative to the support body, wherein the needleshield or a needle shield assembly comprises at least one curvedactuation ramp protruding in a lateral direction (L) perpendicular to acentral axis (A) of the safety device, characterized in that the curvedactuation ramp comprises a first lateral dimension (L1) at a proximalend of the needle shield and a second lateral dimension (L2) exceedingthe first lateral dimension (L1) at a distal end of the needle shield,whereby the resilient arm engages the curved actuation ramp when theneedle shield is slid relative to the support body.
 14. A safety deviceaccording to claim 13, characterized in that the resilient arm is madefrom a plastics material.
 15. A safety device according claim 13,characterized in that the resilient arm is integrally formed to thesupport body.
 16. A safety device according to claim 13, characterizedin that the resilient arm is non-energized in a rest position, whereasthe resilient arm in the rest position extends essentially parallel tothe central axis (A) and over a substantial axial length of the supportbody.
 17. A safety device according to claim 13, characterized in thatthe needle shield is slideable with respect to the support body from aninitial position (I) to a retracted position (II) and further to anadvanced position (III), wherein the needle shield protrudes the supportbody in the initial position (I) and in the advanced position (III) andwhereas the needle shield is substantially received within the supportbody in the retracted position (II).
 18. A safety device according toclaim 17, characterized in that the needle shield in the retractedposition (II) is biased with respect to the support body in a distaldirection by the stressed and energized resilient arm that is bent inthe lateral direction (L).
 19. A safety device according to claim 17,characterized in that the resilient arm is in the rest position when theneedle shield is in the initial position (I).
 20. A safety deviceaccording to claim 13, characterized in that the curved actuation rampis integrally formed to the needle shield.
 21. A safety device accordingto claim 13, characterized in that the needle shield comprises askin-contact flange of increased surface area.
 22. A safety deviceaccording to claim 13, characterized in that the needle shield comprisestwo laterally protruding curved actuation ramps that protrude oppositesides of the needle shield.
 23. A safety device according to claim 13,characterized in that the safety device comprises a substantiallycylindrical outer body that is slideably arranged with respect to thesupport body, whereas the outer body comprises at least one axial slotsized to receive the resilient arm and/or the curved actuation ramp. 24.An injection device (D) comprising a pre-filled syringe with ahypodermic needle attached to a distal end of the pre-filled syringe anda safety device according to claim 13 for the pre-filled syringe,wherein the safety device comprises a substantially cylindrical andhollow support body comprising at least one resilient arm and a hollowneedle shield slideably arranged relative to the support body, whereinthe needle shield comprises at least one curved actuation rampprotruding in a lateral direction (L) perpendicular to a central axis(A) of the safety device, characterized in that the curved actuationramp comprises a first lateral dimension (L1) at a proximal end of theneedle shield and a second lateral dimension (L2) exceeding the firstlateral dimension (L1) at a distal end of the needle shield, wherein theresilient arm engages the curved actuation ramp when the needle shieldis slid relative to the support body, wherein the hypodermic needleprotrudes the distal end of the support body and is surrounded by theneedle shield in an initial position (I) and/or in an advanced position(III).